The Network Topologies
Introduction to Network Topologies –
The Network Topology is defined as the arrangement of network. It includes nodes & connecting lines. Think of a topology as a network’s virtual shape or structure. This shape does not necessarily correspond to the actual physical layout of the devices on the network.
There are two ways of defining network Topology :
- The Logical (or signal) topology
- The Physical topology.
1.The Logical (or signal) Topology –
Logical topology is the way through which the signal act on the network media or data passes through the network from one device to the other without regard to the physical interconnection of the devices. A network’s logical topology is not necessarily the same as its physical topology.
Applications of Logical Topology –
- The original twisted pair Ethernet using repeater hubs was a logical bus topology carried on a physical star topology.
- Token ring is a logical ring topology, but is wired as a physical star from the media access unit.
2.The Physical topology –
The physical topology of a network is the actual geometric layout of workstations. There are several common physical topologies.
Network topologies are categorized into the following basic types:
1.Bus Topology –
The Bus topology is used in local area networks. Each node is connected to a single cable, by the help of interface connectors. This central cable is the backbone of the network known as the bus.
Bus topology is a network type in which every computer and network device is connected to single cable. When it has exactly two endpoints, then it is called as Linear Bus topology.
Key Points –
- It transmits data only in one direction.
- Every device is connected to a single cable.
- It is cost effective.
- Cable required is least compared to other network topology.
- Used in small networks.
- It is easy to understand.
- Cables fails then whole network fails.
- If network traffic is heavy or nodes are more the performance of the network decreases.
- Cable has a limited length.
- It is slower than the ring topology.
2. Ring Topology –
A ring topology is a bus topology in a closed loop. Data travels around the ring in one direction. When one node sends data to another, the data passes through each intermediate node on the ring until it reaches its destination.
- Transmitting network is not affected by high traffic or by adding more nodes, as only the nodes having tokens can transmit data.
- Cheap to install and expand
- Troubleshooting is difficult in ring topology.
- Adding or deleting the computers disturbs the network activity.
- Failure of one computer disturbs the whole network.
3. Star Topology –
A star topology typically uses a network hub or switch and is common in home networks. Every device has its own connection to the hub. The performance of a star network depends on the hub. If the hub fails, the network is down for all connected devices. The performance of the attached devices is usually high, because there are usually fewer devices connected in star topology that in other types of networks.
The cost of setup is higher than for bus and ring network topology, but if one attached device fails, the other connected devices are unaffected.
Key Points –
- Every node has its own dedicated connection to the hub.
- Hub acts as a repeater for data flow.
- Can be used with twisted pair, Optical Fibre or coaxial cable.
- Fast performance with few nodes and low network traffic.
- Hub can be upgraded easily.
- Easy to troubleshoot.
- Cost of installation is high.
- Expensive to use.
- If the hub fails then the whole network is stopped because all the nodes depend on the hub.
4. Tree Topology –
The tree network topology uses two or more star networks connected together. The central computers of the star networks are connected to a main bus. Thus, a tree network is a bus network of star networks.
Key Points –
- Ideal if workstations are located in groups.
- Used in Wide Area Network.
- Extension of bus and star topologies.
- Expansion of nodes is possible and easy.
- Easily managed and maintained.
- Error detection is easily done.
- Heavily cabled.
- If more nodes are added maintenance is difficult.
- Central hub fails, network fails.
5. Mesh Topology –
The mesh network topology employs two schemes, called full mesh and partial mesh. In the full mesh topology, each workstation is connected directly to others. In partial mesh topology, some workstations are connected to others, and some are connected only to those other nodes with which they exchange the most data.
Mesh topology is robust and troubleshooting is relatively easy. However, installation and configuration are more complicated than with the star, ring and bus topologies.
Key Points –
- Fully connected.
- Not flexible.
- Each connection can carry its own data load.
- It is robust.
- Fault is diagnosed easily.
- Provides security and privacy.
- Installation and configuration is difficult.
- Cabling cost is more.
- Bulk wiring is required.
6. Hybrid Topology –
Hybrid networks combine two or more topologies in such a way that the resulting network does not exhibit one of the standard topologies.
Key Points –
- It is a combination of two or topologies
- Inherits the advantages and disadvantages of the topologies included
- Reliable as Error detecting and trouble shooting is easy.
- Scalable as size can be increased easily.
- Complex in design